Move all the tests into the module they are testing.

[ttung]

For example, starfish/test/experiment/builder/* is getting moved to starfish/experiment/builder/test.

This simplifies navigation in the IDE, and also ensures we put the tests in the right place (c.f., all the filter tests in starfish/test/pipeline).

Test plan: make -j fast lint mypy

[codecov-io]

Codecov Report

Merging #1111 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1111      +/-   ##
==========================================
- Coverage   88.91%   88.87%   -0.05%     
==========================================
  Files         168      167       -1     
  Lines        6542     6516      -26     
==========================================
- Hits         5817     5791      -26     
  Misses        725      725

Impacted Files	Coverage Δ
...arfish/spots/_detector/test/test_spot_detection.py	100% <ø> (ø)
...fish/spots/_pixel_decoder/test/test_targets_map.py	100% <ø> (ø)
...ish/imagestack/test/test_imagestack_coordinates.py	96.42% <ø> (ø)
...rfish/multiprocessing/test/test_multiprocessing.py	92.3% <ø> (ø)
starfish/imagestack/test/imagestack_test_utils.py	100% <ø> (ø)
...l_decoder/test/test_calculate_mean_pixel_traces.py	100% <ø> (ø)
...ntensity_table/test/test_intensity_table_coords.py	97.14% <ø> (ø)
starfish/intensity_table/test/test_concatenate.py	100% <ø> (ø)
starfish/codebook/test/test_metric_decode.py	100% <ø> (ø)
starfish/codebook/test/test_from_code_array.py	100% <ø> (ø)
... and 34 more

---

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[kne42]

just saw this but 😍 😍 😍